1. Field
The present invention relates to a refrigerator and a defrost control method thereof, and, more particularly, to a refrigerator and a defrost control method thereof that are capable of sensing the amount of frost formed on an evaporator based on the change amount of absolute humidity in the refrigerator to control a defrost operation.
2. Description of the Related Art
Generally, a refrigerator is an apparatus that supplies cool air, generated when liquid refrigerant is evaporated to absorb the surrounding heat through a refrigeration cycle in which refrigerant circulates, to a food storage chamber, such as a freezing compartment and a refrigerating compartment, to keep various kinds of food fresh for a long time. The freezing compartment is normally maintained at a temperature of approximately −18° C., and the refrigerating compartment is normally maintained at a temperature of approximately 3° C.
The refrigeration cycle includes a compressor to compress refrigerant to a high temperature and high pressure, a condenser to condense the compressed refrigerant through heat exchange between the refrigerant and the surrounding air, a capillary tube to expand the condensed refrigerant to low pressure, and an evaporator to evaporate the expanded refrigerant through heat exchange between the refrigerant and food in the storage chamber. The surface temperature of the evaporator to cool the storage chamber through the refrigeration cycle is lower than the temperature of air in the storage chamber, with the result that moisture condensed from the air in the storage chamber, the temperature of which is relatively high, sticks to the surface of the evaporator, i.e., frost is formed on the evaporator. With the passage of time, the frost formed on the evaporator thickens, with the result that heat exchange efficiency of the refrigerant passing through the evaporator lowers, and therefore, power consumption increases excessively.
In a conventional refrigerator, the operation time of the compressor is integrated, and a defrost heater mounted adjacent to the evaporator is driven to perform a defrost operation, i.e., to defrost the evaporator, when an integrated operation time exceeds a predetermined time, in order to solve the above problem.
In the conventional refrigerator, however, the defrost operation is performed based on the integrated operation time of the compressor, irrespective of the amount of frost formed on the evaporator. As a result, it is difficult to efficiently defrost the evaporator. Also, cooling efficiency lowers due to unnecessary repetition of the defrost operation.
More specifically, moisture in the storage chamber evaporates with the passage of time in a fully sealed state in which a door of the refrigerator is closed, and frost is formed mostly on the evaporator. Consequently, when a large amount of external moisture is introduced into the storage chamber or a large amount of food is stored in the storage chamber, the amount of moisture in the storage chamber increases, with the result that the amount of frost formed on the evaporator increases. In the conventional refrigerator, however, the defrost operation is performed based on the predetermined integrated operation time of the compressor, irrespective of the amount of frost, which is varied depending upon the amount of moisture in the storage chamber. As a result, the defrost operation is not properly performed, and therefore, the frost formed on the evaporator is not fully removed, which lowers cooling efficiency of the refrigerator.
On the other hand, when the amount of moisture in the storage chamber is not large, the conventional refrigerator, which is constructed to perform the defrost operation for the predetermined integrated operation time of the compressor, although the defrost operation is not necessary when the amount of frost formed on the evaporator is small, unnecessarily frequently performs the defrost operation, with the result that power consumption increases excessively. Furthermore, high-temperature heat generated from the defrost heater is introduced into the storage chamber, with the result that cooling efficiency is lowered.